This Phase II, SBIR contract is for the advanced vaccine efficacy studies, which involve TRAMP tumor challenge of vaccinated PSA+ transgenic mice. Engineered for increased immunogenicity PSA variants will be delivered and expressed in PSA+ mice using novel [unreadable]vector VLP[unreadable] (vVLP_ vaccine platform. The latter represent non-replicating virus-like particles configured to encapsidate expression vector for in vivo delivery and expression of engineered PSA genes.